Problem: $ { {-4} \times \left[\begin{array}{rrr}{2} & {2} & {-1} \\ {-2} & {0} & {-2}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-4}\times{2} & {-4}\times{2} & {-4}\times{-1} \\ {-4}\times{-2} & {-4}\times{0} & {-4}\times{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-8} & {-8} & {4} \\ {8} & {0} & {8}\end{array}\right]}$